高指数晶面铂族单金属/双金属纳米粒子的结构稳定性与热稳定性研究

Platinum-group metals have excellent catalytic performance. Due to their rare reserve on the earth and extremely high cost, improving their catalytic activity, stability and utilization efficiency becomes a key issue in the fields of energy resources, chemical industries, and materials. In this project, classical molecular dynamics methods and first-principles calculations will be employed to systematically study the structural and thermal stabilities of platinum-group monometallic and bimetallic nanoparticles with high-index facets. We will first address the relative stability and stabilization mechanism of Pt,Pd monometallic nanoparticles with different high-index facets, and examine the size effects on the stability. Subsequently, the effects of composition and configuration on the stabilities of Pt-Pd bimetallic nanoparticles with high-index facets will be explored. Thermally driven structural changes, especially structural defects, noncrystallization, disordering and locally premelting, will be investigated by analyzing the microstructural evolutions and dynamic behaviors of nanoparticles at different temperatures to shed light on their thermal stability and stabilization mechanism. This project will discover the intrinsic relations between their surface structures and stabilities, and design mono-/bi-metallic nanoparticles with both highly open surface structure and excellent stability, thus provding a theoretical basis for synthesizing nanoparticle catalysts of high performance and low cost.

铂族金属具有优异的催化性能，但资源匮乏、价格高昂。因此，提高它们的催化活性，稳定性和利用效率成为能源、化工和材料领域的重大关键问题。本项目拟采用分子动力学方法结合第一性原理计算，对高指数晶面铂族单、双金属纳米粒子的结构稳定性和热稳定性开展系统的研究；首先研究不同高指数晶面Pt、Pd单金属纳米粒子的相对稳定性和稳定机理，并探讨尺寸效应对稳定性规律的影响；在此基础上，研究不同组分和不同结构的高指数晶面Pt-Pd双金属纳米粒子的稳定性规律；重点分析不同温度下纳米粒子的微结构演化和动力学行为，研究温度改变引起的结构变化，尤其是结构缺陷、非晶化、无序化和局部预熔，阐明纳米粒子的热稳定性及其机理；从原子和电子层次上揭示高指数晶面纳米粒子的表面结构与稳定性的内在关联，筛选和设计具有高开放表面结构和良好稳定性的单/双金属纳米粒子，为制备高性能﹑低成本纳米粒子催化剂提供理论依据。

铂族金属由于具有优异的催化性能而备受关注。本项目采用分子动力学方法结合多种结构优化技术，对一元、二元、三元以及四元铂族金属纳米粒子的稳定性进行了系统的研究。其中，一元金属涉及高指数晶面Pt、Rh纳米粒子和多面体单晶及孪晶Au纳米粒子；二元金属涉及PtPd、PtAu、AuPd、PdNi等纳米粒子；三元金属包括PtCuAu、PtPdRh、PtPdAu等纳米粒子；四元金属涉及PtPdCuAu纳米粒子。这些纳米粒子的稳定性研究涉及到它们的结构稳定性、热稳定性和形状稳定性研究。研究的结果显示：纳米粒子的稳定性与金属元素的成分及分布，粒子的表面结构和粒子的尺寸密切相关；纳米粒子中因组分元素的晶格常数、结合能、空位形成能和表面能的差异，在升温过程中金属原子会发生重新排布；纳米粒子中元素的种类与分布，以及粒子的结构和形态对熔化的起源和演化机制有重大影响。本项目的研究从原子尺度上揭示了纳米粒子的稳定性与其结构、元素成分和分布之间的内在关联，为制备高性能、低成本纳米粒子催化剂提供了理论指导和参考意义。